The present invention relates to a hard endoscope oblique view type which permits the illumination to lighten equally the visible range.
In recent years, endoscopes are widely employed for inspecting and diagnosing the intracavitary organs, intraorganic wallsurface or other objectives by introducing a tubular insert into the corporal cavity. Also in industrial field, endoscopes are employed to inspect inside of the tubes of boiler, machines, chemical plants etc.
These endoscopes include structurally the illuminating optical system for ejecting the illuminating light from the objective side of the top end of housing after transmitting the illuminating light supplied to the observer's side when having inserted the tubular housing, and the inspecting optical system for inspecting from the rear of the eye-piece on the observer's side through the image-transmitting means after having focussed the image of objective illuminated by said illuminating optical system.
In order to inspect appropriately according to the object in a desired region through the openings at respective top ends of said illuminating optical system and the inspecting optical system; the endoscopes for inspecting axial direction in front of the tubular housing through the inspection opening with the illuminating light are classified into the direct view type formed opposite to the object, the lateral view type formed along the lateral of the tubular housing and the oblique view type inclined with a predetermined angle to the axial direction of the tubular housing.
The tubular housing of the endoscope formed with an opening for inspecting each direction of view field, when inserted by the guides of soft endoscope with a flexible tubular housing and of trachea etc., is sometimes formed rigid in a substantially linear shape to facilitate its introduction into the cavity.
In the hard endoscope of oblique view type, in view of conventional techniques, the inner tube is passed through with the outer tube having the inspecting optical system inside, while the illumination-transmitting means is passed through the cavity of substantially crescent cross section between the circumference of the outer tube and the outer circumference of said inner tube. The present endoscope is so composed that the object illuminated with the light ejected from the top end surface of said transmission means may be inspected with said inspecting optical system. However, in the endoscope of oblique view type as disclosed in said conventional techniques or in Japanese Pat. Application Disclosure No. 12,642/58, the illuminating light ejected from the top end of the illumination-guiding fiber as the transmission means for inspection-range directed to the front of oblique direction is diffused too much in the direction curved obliquely and cannot illuminate equally the inspection range. Accordingly even if the image of the object is caught in the field of view, it is often difficult to inspect sufficiently clearly and so a diagnose is a little difficult. In this way, the function of the inspecting optical system is insufficiently performed, but a highly complete endoscope of oblique view type is required. Furthermore it is difficult to maintain the axial direction of illumination with high accuracy from view-point of the production of endoscope.